introduce `wp core multisite-install` (doesn't work yet)
skip ms_site_check() when installing
test both with and without multisite constants scenarios
copy the missing steps from populate_network()
fake $current_site and $current_blog globals
fix edge case in guess_url()
move set_url_params() to WP_CLI\Runner

It wasn't really meant to be a public utility. We just didn't have a
runner class back then.
move docs for multisite-convert
get rid of some DB warnings
define COOKIEHASH to get rid of DB warning

That's because wp_cookie_constants() goes looking for siteurl in the
not-yet-existing wp_sitemeta table.
behat: remove mismatched URL
account for already defined multisite constants
add docs for 'core multisite-install'
make --title optional for multisite-convert

use the same logic from /wp-admin/network.php
don't fail if the site is already installed
merge master into multisite-install branch
Merge pull request #598 from wp-cli/multisite-install

Introduce command to install multisite from scratch